Today's telecommunication environment is moving from a static, fixed and reliable base, whose cornerstone is physical connectivity, to a mobile, unwired base that hopes to provide the quality, reliability and comparable data bandwidths of the former. As seen in the evolution of the low bandwidth, ground-based cellular network over the last ten years, that goal may not be attainable other than in theory. The key to reaching the service and reliability levels of fixed land lines depends on providing extensive overlapping coverage across every part of a user coverage area.
As shown during the cellular era, that can be a very difficult requirement to satisfy, since the user does not always remain within the bounds of the most probable coverage area of metropolitan centers, interstate highways, etc. If population patterns persist as they have since the beginning of time, where 100 percent of the world's population has inhabited only fractional percentages of the total landmass, it appears that a compromise is in order. The arrival of the ‘hotspot’ appears to have changed the landscape for wireless connectivity and the rush is on to huddle the masses of individual users underneath various ‘umbrellas’, i.e., within range of the nearest access point at logical places where people congregate—football stadiums, coffee shops, airport lounges, hotels and the like.
The logical next step is to make the ‘umbrellas’ larger and larger until they encompass an entire metropolitan area, with less than optimum residual benefits to the potential millions of non Line of Sight (LOS) users within a large 30 mile coverage area, even using the latest adaptive antenna array and diversity techniques. This is due to the projected deployment of far fewer base stations (compared to an equivalent metropolitan cellular infrastructure) as inferred in the implementations of the IEEE standards 802.16/802.20 for Metropolitan Area Networks (MAN).
Another approach is a combination of limiting the size of the cells and overlapping them throughout the metropolitan area—one of the interpretations of the IEEE 802.16e standard, which is primarily focused on non LOS mobile users. When combined with backhaul capability from the smaller ‘hotspot’ feeders such as those derived from the IEEE 802.11b/a standards, using 802.16a techniques for backhauling into fixed infrastructure, a positive improvement in bandwidth and less expensive deployment over continued cellular infrastructure expansion is possible within the metropolitan ‘umbrella’.
Until deployment and coverage is complete within the MAN coverage area using this method, there will be many holes where dropouts may occur. It would be very likely that broadband quality data transfers would frequently be interrupted early on in this environment. In the case of public safety vehicles requiring critical updates or downloads such as high quality streaming video feeds with minimum latencies, or large transportation vehicles such as trains, busses and aircraft accommodating a multi-user environment over a long period of time, a logical and seamless handoff coordination and connect/re-connect method could be crucial to the MAN's success, particularly when outside coverage areas, both within the network while scaling up deployment and in transitioning between MANs once deployments are considered complete.
Before the goal of providing optimum broadband speeds while roaming between hotspot coverage areas can be reached in a way where deployment can be optimized, the hierarchy within the customer base must first be established. Should deployment be based on the number of individual customers within a metropolitan area, each with a variety of mobile devices requiring frequent updates, and each with a different level of perceived urgency and importance placed on the frequency of updates to their unwired devices? The individual customer may even insist and demand continuous and seamless connectivity. Should you start with the local municipality's needs, or even the federal government's? Is it more critical to provide services for transportation vehicles operating in a controlled or semi-controlled environment, as in the case of busses, trains, planes, ships and public safety vehicles, than it is to cater to the predictably random nature of an individual user, clustered in population enclaves?
In an ideal world the majority of projected users should dictate how and where coverage is required, assuming that coverage would ultimately be pervasive and seamless. One type of technology accommodating one primary type of customer (the individual user) can never meet all demands, due to physical limitations such as accessibility considerations caused by perturbations in the landscape, the clustering tendencies of mankind and many other criteria which demand flexibility, scalability and backwards compatibility to existing infrastructures.